The primary objectives are to investigate the relationships of metallothionein (MT) to zinic metabolism, determine the influence of dietary factors on the half-lives of MT species, determine the effects of various stresses on MT levels, study the induction of MT by heavy metals in zinc deficient rats, study the accumulation of zinc in cellular fractions and in soluble proteins in the cytosol from tissues of pigs and lambs fed various zinc levels in the diet, and to characterize a low molecular weight zinc containing peptide from rat kidneys. The previous work on the half-lives of MT was done with a mixture of MTs. In the present studies we propose to inject rats with 14C-cystine, isolate the individual MT species, and determine their radioactive contents. Our preliminary work indicates that zinc is absolutely essential for the induction of MT, and further studies are planned with zinc deficient rats. Since we showed that zinc accumulated only in MT of the soluble proteins in the tissue cytosols from rats when this metal was put in the diet, we want to determine whether this type of relationship exists in other species of animals. The low molecular weight zinc containing peptide is present in kidneys, but not liver, when rate are fed a diet containing either high levels of zinc or cadmium. Zinc is apparently necessary for its synthesis since it was not present in rat kidneys of zinc deficient rats fed a diet with cadmium. It is anticipated that its characteristics will offer some clues on its metabolic functions.